Recording information by means of a photosensitive material of biological origin

ABSTRACT

A photographic recording material which comprises a support bearing at least one photosensitive layer containing photoactive protochlorophyll(ide)-apoprotein complex, which, by exposure to light of the wavelength region absorbed by the complex in a pattern representing information to be recorded, forms a corresponding pattern of differentiations in light-absorption and fluorescence emission characteristics.

Elite tates tet 1 ujardin et 211.

1 1 *Dec. 2, 1975 l l RECORDING INFORMATION BY MEANS OF A PHOTOSENSITIVEMATERIAL OF BIOLOGICAL ORIGIN [76] Inventors: Esther Dujardin, (1)Avenue des Bois 8, 4050, Mery-Esneux; Ysbrand Kuiper, (2) Grammerode 21,B 3800, St. Truiden; Rene Cremer, (3) Avenue des Tilleuls 2, B 4000,Liege; Cyrille Sironval, (4) Avenue des Bois 8, B 4050, Mery-Esneux, allof Belgium [*1 Notice: The portion of the term of this patent subsequentto Mar. 18, 1992, has been disclaimed.

[22] Filed: Jan. 24, 1973 [21] Appl. No.: 326,185

[521 U.S. C1 96/48 R; 96/88; 260/112; 260/6; 260/8; 106/124; 106/157;117/34 [51] Int. Cl. G03c l/00; G03c 5/24 [58] Field of Search 96/88, 48R; 260/112. 6. 260/8; 106/124. 157: 117/34 [56] References Cited OTHERPUBLICATIONS Smith, ct al.: Nature, 178. (1956). 751-752.

Primary E,\'aminerWon H. Louie. Jr. Attorney. Agent, or Firm-Ernest G.Montague; Karl F. Ross; Herbert Dubno [57] ABSTRACT A photographicrecording material which comprises a support bearing at least onephotosensitive layer containing photoactiveprotoch1orophyll(ide)-apoprotein complex, which. by exposure to light ofthe wavelength region absorbed by the complex in a pattern representinginformation to be recorded. forms a corresponding pattern ofdifferentiations in lightabsorption and fluorescence emissioncharacteristics.

5 Claims, 2 Drawing Figures US. Patent Dec.2,197 5 Sheet10f2 3,923,516

Fig. I

US. Patent Dec. 2, 1975 Sheet 2 5m 3,923,516

F Fig. 2

RECORDING INFORMATION BY MEANS OF A PHOTOSENSITIVE MATERIAL OFBIOLOGICAL ORIGIN This application is related to application Ser. No.326,442 filed concurrently herewith and so referred to below.

The present invention relates to a method of recording and reproducinginformation wherein use is made of a photosensitive substance ofbiological origin and to photosensitive elements comprising saidsubstance. The photosensitive substance of biological origin is moreparticularly an apoprotein-protochlorophyll(ide) complex isolated frometiolated angiosperm plants.

It is known that dark-grown (etiolated) plants undergo spectral changesunder the influence of light. By brief illumination of the etiolatedleaves the initial absorption maximum in the red region of the spectrumis irreversibly shifted from about 647 to about 676 nm and the initiallow temperature fluorescence emission maximum in the red region of thespectrum is irreversibly shifted from about 657 to about 688 nm.

The protochlorophyll(ide) which has accumulated in the dark-grown plantsand which is the direct precursor of the chlorophyll found in normalgreen chloroplasts is responsible for the above phenomenon byphotoreduction of the protochlorophyll(ide) to chlorophyll- (ide).

Essential for the photoreduction of the protochlorophyll(ide) tochlorophyll(ide) is a specific binding with an apoprotein. This binarycomplex of protochlorophyll(ide) with apoprotein has been termedprotochlorophyll(ide) holochrome.

The isolated protochlorophyll(ide) holochrome extracted from theetiolated plants as described in the literature is unstable in the sensethat it is photoactive only if it is kept in the dark at a temperaturebelow C., and the photoactivity is only retained for an appreciablelength of time, say some weeks or months, if the holochrome is stored ata temperature appreciably below 0C.

The present invention is based on the idea of rendering aprotochlorophyll(ide) holochrome isolated from etiolated plants stableat room temperature or converting it to a form which remains photoactiveat roomtemperature, and on the idea of forming a photographic recordingmaterial comprising the said isolated holochrome as the photosensitivesubstance, the recording medium being suitable for use in the recordingof graphic and other information by information-wise exposure of thesaid material, i.e. exposure to light in a pattern representinginformation to be recorded.

Accordingly, the present invention provides a photographic recordingmaterial which as broadly defined comprises a support bearing at leastone photosensitive layer containing photoactive protochlorophyll(ideapoprotein complex which by exposure to light of the wavelength regionabsorbed by said complex in accordance with information to be recorded,forms a pattern of differentiations in light-absorption and fluorescenceemission representing the recorded pattern.

The present invention further provides a method of recording informationwhich as broadly defined comprises exposing a photosensitiveprotochlorophyll(ide)- apoprotein complex, to light of the wavelengthregion absorbed by said complex in accordance with an informationpattern, so as to cause on the exposed areas a change in the absorptionand fluorescence emission characteristics so that a pattern is formed ofinformation-wise differentiations in light-absorption and fluorescenceemission.

Therefore the photoactive protochlorophyll(ide)- apoprotein complex usedas photoactive substance in accordance with the present invention ispreferably such that it retains its photoactivity for substantialperiods of time, e.g., at least some weeks and preferably at least somemonths, at room temperature.

The maintenance of long-term photoactivity at room temperature isstrictly dependent on the absence of free water in theprotochlorophyll(ide)-apoprotein complex. The complex should thereforebe substantially dehydrated, e.g. by lyophilization as describedhereinafter.

A photoactive protochlorophyll(ide)-apoprotein complex which isparticularly suitable for use as a photoactive ingredient in aphotographic recording material in accordance with the invention can beobtained by extracting protochlorophyll(ide)-apoprotein complex frometiolated plant material and precipitating the complex with the help ofa natural or synthetic polymeric material, e.g., polyethylene glycol,dextran, antibodies, etc. The resulting material is a ternary complex ofthe isolated protochlorophyll(ide)-apoprotein binary complex with anatural or synthetic polymeric material but it is not known whether thepolymeric material actually forms a part of the complex or whether thepolymeric material is merely in association with the binary complex andtherefore the term ternary complex is used loosely and should beunderstood as referring to the photoactive product isolated from theetiolated plant material and complexed or in association with the saidnatural or synthetic polymeric material.

Such a ternary complex remains photoactive when kept in the dark attemperature below 0C., preferably below-10C. but above thesetemperatures, owing to a denaturation of the protein, it graduallylooses its photoactivity so that at a temperature of 23C. it completelyloses all photactivity after a few days. Therefore, in order to remainphotoactive at room temperature and thus to be suitable for use in therecording of information at room-temperature, the formed complex shouldbe dehydrated.

For a better understanding of the present invention, the absorption andfluorescence emission characteristics of theprotochlorophyll(ide)apoprotein complex will now be described in detail.

The protochlorophyll(ide)-apoprotein complex isolated in photoactivecondition from etiolated plants loses all photoactivity at temperaturesbelow l00C., e.g. at the temperature of liquid nitrogen (-l96C.), butregains its photoactivity when brought to normal temperatures again. Thenon-exposed complex has an absorption spectrum with a maximum in theU.V.-blue region of the spectrum (at about 436 nm) and a maximum in thered region of the spectrum, which slightly varies according to thecircumstances of isolation, and is between about 635 and about 645 nm.The absorption band with maximum in the red region of the spectrum has acorresponding fluorescence emission maximum between about 645 and about655 nm.

When the photoactive complex is completely photoconverted, thefluorescence emission band is shifted towards the longer wavelengthswith a maximum at about 688 nm; the corresponding absorption band isalso shifted towards the longer wavelengths. Moreover, byphotoconversion the intensity of absorption is markedly reduced in theU.V.-blue region (at 436 nm) and markedly increased in the red region.

When before photoconversion, the complex is partly denaturated, theunexposed photoactive complex not only has a fluorescence emissionmaximum at about 645-655 nm owing to the remaining photoactive complexbut also a fluorescence emission maximum at about 625-630 nm resultingfrom photo-inactive protochlorophyll(ide) apoprotein formed bydenaturation. Thus with the initially photoactive complex, whendenaturated before photoconversion, there is a shift from thefluorescence emission maximum at about 645-655 nm to a fluorescenceemission maximum at about 625-630 nm. When the partly denaturatedcomplex is exposed to effect complete photoconversion of the remainingphotoactive complex, the exposed complex has a fluorescence emissionband with maximum at about 625-630 nm owing to the photo-inactivecomplex and a fluorescence emission band with maximum at about 688 nmowing to the photoconverted complex.

By denaturating the photoexposed complex, the fluorescence emission bandwith maximum at about 688 nm of the photoconverted complex shifts to theshorter wavelengths to form a fluorescence emission band with maximum atabout 670 nm.

The absorption bands corresponding with the above fluorescence emissionbands are some 2 to 15 nm in the shorter wavelength region.

The above changes in absorption and fluorescence emissioncharacteristics under the influence of light, of theprotochlorophyll(ide)-apoprotein complex isolated in photoactivecondition from etiolated plant material can be used for the recorsingand reproduction of information in a method according to the presentinvention.

Information-wise exposure of the photosensitive complex should occurwith light sources emitting light of the wavelength region absorbed bythe complex. Since the complex has an absorption spectrum extending fromthe U.V.-blue region of the spectrum to the red region of the spectrum,exposure may occur by means of light sources of the polychromatic typee.g. ordinary daylight, xenon gas lamps, incandescent bulbs,photographic flash units and the like and lightsources of themonochromatic type, e.g. monochromatic U.V.-blue light and monochromaticred light including lasers.

The information-wise exposure applied in the present invention may be acontact exposure as well as an optical-projection exposure as is usede.g. in an optical enlarging apparatus. The information-wise exposureneed not be simultaneous in all parts of the complex. The exposure maybe progressive in a continuous step as in sound track recording or insuccessive intermittent steps provided that the requiredinformation-wise change is obtained. Thus, thecomplex may be scannedwith an image-wise modulated radiant energy spot of high intensity e.g.a laser beam, or the complex may be progressively exposed through a slite.g. exposed to copying light of a tubular lamp that is given atranslation movement along the original.

The information to be recorded may be of any desirable type, e. g.information in the form of images, codemarks, dots and lines,alphanumerical writing, etc.

The recorded information can be retrieved, i.e. reproduced, as describedhereinafter provided the recorded information is fixed.

Fixing may occur in various ways, e.g. by selective removal of theexposed or non-exposed complex, by selective removal of the pigment ofthe exposed or nonexposed complex, or by such physical or chemicaltreatment that the photoconversion of non-exposed complex is inhibitedtemporarily or permanently.

A very convenient way of permanently fixing the information-wise exposedcomplex is to denaturate the protein-material in the complex, e.g. by aheat treatment, by humidification, by an acid-treatment with acids insolution or vapor form, Reversible fixing of the recorded information,which means that the unexposed complex is temporarily renderedinsensitive to actinic light exposure, can be suitably effected bysubjecting the exposed material to such low temperature that it is nolonger photosensitive, say below l0OC., e.g. the temperature of liquidnitrogen(-l96C.).

The temporary fixing of the recorded information offers the possibilityof recording supplemental information. For instance, afterinformation-wise exposure, the complex is kept at very low temperature,e.g. that of liquid nitrogen, so that the recorded information can beretrieved at this temperature. Then the complex can be further exposedinformation-wise when bringing the complex to normal temperature. Thisprocedure can be repeated as many times as desired by keeping theternary complex between the successive information-wise exposures atvery low temperatures. Finally all successive informations can bepermanently fixed by one of the methods described above.

When the information-wise exposed complex has been fixed to renderfurther phototransformation of the non-exposed areas impossible, readingof the recorded information can be repeated as often as desired. Readingconsists in distinguishing a differentiation in absorption or influorescence emission characteristics.

Retrieval of the recorded information as a pattern of infonnation wisedifferentiations in absorption or fluorescence emission can occur bymeans of appropriate filters.

in retrieving the recorded information it is possible to utilize thedecrease in absorption intensity for the UV.- blue region of thespectrum or the increase in absorption intensity for the red region ofthe spectrum on the exposed areas as compared with the non-exposedareas. For this purpose, filters can be used absorbing all light of thewavelength region not considered and preferably transmitting only lightof the wavelength region considered.

However, retrieval of the recorded information is preferably based onthe shift by the photoexposure of the absorbtion band or correspondingfluorescence emission band in the red region of the spectrum. For thispurpose, cut off filters can be used which transmit or absorbsubstantially all light of a wavelength below the red absorption bandor'fluorescence emission band of the exposed areas, or interference orband filters can be used which transmit or absorb substantially alllight of the wavelength of the red absorption band or fluorescenceemission band of the exposed areas only or unexposed areas only. Inretrieving the recorded information it is also possible to usemonochromatic coherent radiation sources, the radiation of which isabsorbed only by the exposed or non-exposed areas.

According to an interesting embodiment of the present invention therecorded information is retrieved by utilizing the shift in fluorescenceemission rather than the shift in absorption. For this purpose, afterinformation-wise exposure of the complex and treatment thereof to renderfurther phototransformation impossible, the complex is overall exposedto light of the ab sorption region of the complex e.g. U.V.-blue lightwhich stimulates the fluorescence in the form of information-wisedifferentiations in fluorescence which can be retrieved as describedabove by means of an appropriate filter. Since in the exposed areas, theintensity of absorption for the U.V.-blue region of the spectrum hasdecreased, the overall exposure of the informationwise exposed and fixedcomplex to U.V.-blue light will result in a higher excitation of thefluorescence emission on the non-exposed areas as compared with theexposed areas.

The recorded information can be read visually, scanned by means of anappropriate instrument or recorded by means of other photosensitivesystem, e.g. silver halide photography.

The amount of detectable differentiation in absorption and fluorescenceemission is proportional to the intensity of the exposure. This meansthat as the intensity of the exposure or the exposure time increases,the amount of transformed complex per unit of exposed area increaseswhich results in an increased differentiation in absorption andfluorescence emission characterictics. However, exposure times as low asl millisecond by means of ordinary photographic flash units suffice forrealizing a detectable change in absorption and fluorescence emissioncharacteristics. When the expo sure occurs by means of laser light,exposure times of less than 1 millisecond suffice.

Since the amount of detectable differentiation in absorption orfluorescence emission characteristics is proportional to the intensityof the exposure it is possible by modulation of the exposure radiationto record data in analogon form. This ressembles quite well photographicimage recording by means of silver halide elements and magnetic soundrecording. As a matter of fact with audiomodulation of the exposureradiation the method of the present invention can be used for producingsound records. These records can then be reproduced through conventionalelectronic means including photocells, amplifiers, etc. The method ofthe present invention can thus be used in any process wherein use ismade of a change in optical density to alter an electric signal, e.g.,electronically recording and reproducing images and sound, recording andreproducing numerical data, etc.

The photoactive ternary complex described above which is preferably usedaccording to the present invention can be obtained by the followingsteps: extraction of the protochlorophyll(ide)-apoprotein complex frometiolated (dark-grown) plants, more particularly from the leaves, buds,petioles, stem, branches, twigs and seeds of higher angiosperrn plants,e.g. leguminous plants such as beans and peas and graminaceas such asbarley and maize, homogenizing the plant material with a buffersolution, filtering the homogenate by squeezing through a fine-wovencloth and centrifuging the filtrate, admixing with the supernatantliquid the natural or synthetic polymeric material thus causing theternary complex to precipitate and collecting the precipitate bycentrifuging.

The etiolated plant material from which the protochlorophyll(ide)-apoprotein complex should be extracted, is ground in a dark coldroom in the presence of a buffer maintaining the pH between 7 and 10 anda compound protecting the protein against oxidation or denaturation e.g.glycerol, polyvinyl 'pyrrolidone, triethanolamine and saccharose. Theamount of buffer and protective agent used is such that the volume to beground is kept as low as possible. Grinding may be done manually in amortar or by means of a mechanical or electric grinder provided noactive radiation is emitted by the mechanism and motors used.

The coarse debris is removed from the homogenate by filtering through afilter with large pores e.g. by squeezing through a cloth whereupon thefiltrate is centrifuged e.g. for 30 to minutes at speeds in the order of5,000 to 30,000 g, or even more dependent on the viscosity of themedium. The supernatant liquid containing the photoactiveprotochlorophyll(ide) apoprotein complex is collected and used toprepare the ternary complex.

The ternary complex of protochlorophyll(ide)- apoprotein with apolymeric material is formed by addition to the supernatant liquid ofany polymeric material including a proteinaceous material that iscapable of forming a precipitate with the protochlorphyll(ide)apoprotein. The precipitate of so-called *ternary" complex is thencollected by centrifugion.

All solutions and equipment used during the extrac tion of the binarycomplex and the formation of the ternary complex are kept at lowtemperature, say below 5C. Whenever vision is necessary, a dim greensafelight may be used during these operations as well as duringetiolation.

The green safe-light should be of low intensity and emit mainlyradiations within the region of 500 to 600 nm, which do not causephototransformation of the photoactive protochlorophyll(ide)-apoproteincomplex which has its main absorption in the U.V.-blue re gion (maximumat about 436 nm) and red region (maximum at about 647 nm in the plantmaterial and at 635-645 nm for the extracted binary complex as well asthe ternary complex formed).

The ternary complex can be stored for several months in photoactivecondition when kept at temperatures below 0C., preferably below 10C.e.g. at 15C. However, at room temperature it looses its photoactivityafter a day or two. As already noted above, the maintenance of long termphotoactivity at room temperature is strictly dependent on the absenceof free water in the protochlorophyll(ide)-apoprotein complex, andtherefore, in order to remain photosensitive at room temperature, theternary complex is dehydrated e.g. by lyophilization.

Thus, for use in accordance with the present invention in order torecord information the photosensitive ternary complex should be storedat temperatures below 0C, and/or dehydrated.

For recording information the photosensitive ternary complex can beapplied to a suitable transparent or opaque support material, e.g. apaper, glass, metal or synthetic film forming support material. Thephotosensitive ternary complex may be lyophilized before or afterapplication to the support. It can be applied as a single coating or asseveral coatings one above the other. The support material can be of anyshape, e.g. sheets, dials, tapes, drums, tridimensional objects, etc.

Since for recording at ordinary temperature, the photosensitive ternarycomplex should in practice be protected against the harmful effect ofmoisture, the sup port material is preferably a water-impermeablefilmforming plastic material e.g. cellulose esters such as cellulosetriacetate, polyvinylacetate, polystyrene, polyethylene terephthalateand related resinous materials or an a-olefin coated paper e.g. papercoated with polyethylene or polypropylene. For the same purpose thecoating of ternary complex is preferably overcoated, eg by spraying,with a protective waterimpermeable coating of a hydrophobic polymericmaterial. Polymers that shield as much as possible the ternary complexfrom direct-contact with the atmosphere include polymers and copolymersof styrene, vinyl acetate, acrylonitrile, acrylic acid esters,methacrylic acid esters and butadiene, hydrophobic cellulosederivatives, phenoxy resins or polycondensates of the polyester typee.g. polycarbonates, etc.

The above hydrophobic protective coatings also protect the recordedinformation against deterioration owing to photooxidation. As a matterof fact. when not shielded against aerial oxidation, the permanentlyfixed information-wise exposed ternary complex should be stored in thedark.

It is evident that all materials used in the composition ofphoto-sensitive elements comprising the photosensitive complex shouldnot affect distinguishing of the information-wise differentiation influorescence emission and absorption characteristics and thereforeshould preferably be colorless and nonfluorescent.

The following Examples illustrate the present invention. The Examplesare given with reference to the accompanying drawing of which FIGS. 1and 2 are spectra illustrating the invention.

EXAMPLE 1 A copper plate was cove red with ordinary filter paper ontowhich was placed a piece of 0.2 mm thick cardboard with a rectangularopening. The opening was filled uniformly with photosensitive ternarycomplex of protochlorophyll(ide)-apoprotein and polyethylene glycol,obtained as described in preparation 1 of the copending applicationfiled on even date herewith for Photosensitive material of biologicalorigin thus forming a photosensitive coating of approximately 0.2 mmthickness.

The whole was lyophilized for 3 days at a temperature of -l3C and avacuum of 2 microns of mercury.

The layer of photosensitive ternary complex was exposed through adensity wedge composed of areas with density 0.1, 0.5 and 1 respectivelywhich was placed in contact with the photosensitive coating. Exposure occurred by means of a Multiblitz 50 electronic polychromatic flash (1/700see-160 Ws) marketed by Gesellschaft fur Multiblitz-Geratc, Dr.IngMannesmann, Porz-Westhoven, Germany, placed at a distance of 50 cmfrom the photosensitive coating.

in order to avoid further phototransformation the exposed plate wasplaced in a Dewar flask in liquid nitrogen medium. Through a window ofthe Dewar Flask, the exposed ternary complex was exposed to radiationsof a mercury vapor lamp through a band filter with peak transmission at442 nm, a bandwidth at half peak transmission from 422 to 472 nm and abandwidth at one/tenth peak transmission from 416 to 490 nm. Thefluorescence pattern formed by the exciting radiation was observedthrough an interference filter with peak transmission at 660 nm, abandwidth at half peak transmission from 657 to 663 nm and a bandwidthat one/tenth peak transmission from 655 to 665 nm. The areas of theexposed coating corresponding with the density areas 1, 0.5 and 0.1 oithe density wedge clearly show a proportional intensity of fluorescenceemission. The area corresponding to the area of density 1 showing themost intense fluorescence emission and the area corre sponding with thearea of density 0.1 showing the least intense fluorescence emission.

When photographing the fluorescin g pattern through the saidinterference filter by means of an ordinary camera loaded with a highspeed silver halide film (exposure time 2 min.) a direct-positive printof the density wedge was obtained.

EXAMPLE 2 Several lyophilized plates were made as described in Example 1which were stored in light-tight metal boxes at 10C in an atmospherewhich was kept dry by means of calcium chloride.

Six plates were taken and exposed through the density wedge of Example 1to an increasing number of flashes; the first plate, plate A receivedone flash as described in Example 1 and the sixth plate, plate Freceived six flashes. The intensity of exposure thus increases from 1 to6 which simulates a modulation of the doses of illumination.

The exposed plates were placed in a Dewar flask as described in Example1 and the fluorescence emission spectra of the three areas of thevarious exposed plates were recorded as described by C. Sironval et al.,Photosynthetica 2 (4), 1968, 268-287 for etiolated leaf samples.

The spectra of plate A show that for the area corresponding with density0.1 of the density wedge, the fluorescence emission maximum at 688 nm ishigher than that of the area corresponding with density 0.5 of thedensity wedge, which in its turn is higher than that of the areacorresponding with density 1 of the density wedge. This means that thefluorescence emission intensity at 688 nm is proportional to theexposure intensity and that there is a sufficient contrast between thearea corresponding with density 0.1 and the area corresponding withdensity 1.

The spectra of the other plates which received an increasing number offlashes shown the same phenomenon wherein the difference betweenfluorescence emission maxima of the areas corresponding to the differentdensity areas of the density wedge decreases as the number of flashesincreases. In FIG. 1 of the accompanying drawings the fluorescenceemission spectra (relative fluorescence l=F versus wavelength =.nm) aregiven of plate E which was exposed to five flashes. Curves 1, 2 and 3are the fluorescence emission spectra of the areas corresponding to theareas with density 0.1. 0.5 and 1 respectively of the density wedge.These spectra show that even after five flashes the area correspondingwith density 0.1 has the highest maximum at 688 nm and the lowestmaximum at 647 nm whereas the area corresponding to density 1 has thelowest maximum at 688 nm and the highest maximum at 647 nm.

EXAMPLE 3 Example 2 was repeated with the difference that after exposurethe plates were not placed in the Dewar flask but heated for 20 min. at60C to effect denaturation of the protein material.

The fluorescence emission spectra of the various plates were recordedand showed the same phenomenon as described in Example 2 with thedifference that the fluorescence emission maxima are at about 628 nm andabout 670 nm. The areas corresponding with density 1 show the highestmaximum at 628 nm and the lowest at 670 nm whereas the areascorresponding with density 0.1 show the highest maximum at 670 nm andthe lowest at 628 nm. In FIG. 2 of the accompanying drawing thefluorescence emission spectra (relative fluorescence l=F versuswavelength 1=nm) are given of plate E which was exposed to five flashes.Curves l, 2, and 3 are the fluorescence emission spectra of the areascorresponding with density 0.1, 0.5 and 1 respectively.

EXAMPLE 4 To a cellulose triacetate support a coating of 1 mm of ternarycomplex, freshly prepared according to preparation 1 of the copendingapplication filed on even date herewith for Photosensitive material 'ofbiological origin, was applied by means of a spatula.

The material was exposed at an ambient temperature of C through anoriginal placed in contact with the photosensitive material. Exposureoccurred for 1 second by means of a projection apparatus the lamp ofwhich is situated at a distance of 1 meter from the original andphotosensitive material. The projection apparatus used was fitted with a24 V/250 W lamp and a lens with focus of 250 mm.

The exposed material showed image-wise differentiations in absorption inthe red region of the spectrum the exposed areas having an absorptionmaxima at about 675 nm and the unexposed areas having an absorptionmaxima at about 640 nm.

The exposed material was placed in contact with a light-sensitive silverhalide material and the latter material was exposed through the firstmaterial by means of a conventional enlarging apparatus, as used insilver halide photography, which was provided with an interferencefilter with peak transmission at 680 nm, a bandwidth at half peaktransmission from 676 to 686 nm and a bandwidth at one/tenth peaktransmission from 673 to 690 nm. The exposure light was thus fullyabsorbed by the exposed areas of the ternary complex but transmitted bythe unexposed areas of the ternary complex so that the silver halidematerial was exposed at the areas corresponding to the non-exposed areasof the ternary complex.

After conventional development of the silver halide material, a positiveprint of the original was obtained.

We claim:

1. Photorecording material comprising a support coated with aphotographic sensitive layer consisting essentially of aphotographically active product formed by:

extracting from an etiolated plant material a photoactiveprotochlorophyll(ide)-apoprotein binary complex with a buffer solutionat a pH between 7 and 10 in the presence of an agent to protect theapoprotein against denaturation at a temperature of at most 5C; addingto said binary complex at a temperature of at most 5C a natural orsynthetic polymeric material selected from the group consisting orpolyethylene glycol, polyvinylpyrrolidone, triethanolamine, saccharoseand dextran to form a precipitate;

cold-centrifuging said precipitate to form a product which is either incomplex or in association with said polymeric material; and lyophylizingsaid product at a. temperature of at most 5C so that the dried finalproduct remains photoactive at room temperature, said product forming apattern by information-wise exposure to light of information-wisedifferentiations in lightabsorption and fluorescence emissioncharacteristics. 2. The photographic recording material defined in claim1 wherein said polymeric material is polyethylene glycol.

3. The photographic recording material defined in claim 1 wherein saidsupport is: a transparent sheet.

4. The photographic recording material defined in claim 1 wherein saidsupport is an opaque sheet.

5. A method of recording information which comprises information-wiseexposing a photosensitive product to light of a wavelength rangeabsorbed by said product to produce thereby a pattern of informationwisedifferentiations in light-absorption and fluorescence-emissioncharacteristics, said productbeing obtained by the steps of:

extracting from an etiolated plant material a photoactiveprotochlorphyll(ide )apoprotein binary complex with a buffer solution ata pH between 7 and 10 in the presence of an agent to protect theapoprotein against denaturation at a temperature of at most 5C; addingto said binary complex at a temperature of at most 5C a natural orsynthetic polymeric material selected from the group consisting ofpolyethylene glycol, polyvinylpyrrolidone, triethanolamine, saccharoseand dextran to form a precipitate;

cold-centrifuging said precipitate to form a product which is either incomplex or in association with said polymeric material; and

lyophilizing said product at a temperature of at most 5C so that thedried final product remains photoactive at room temperature, saidproduct forming a pattern by information-wise exposure to light ofinformation-wise differentiations in lightabsorption and fluorescenceemission characteristics.

1. PHOTORECORDING MATERIAL COMPRISING A SUPPORT COATED WITH APHTOGRAPHIC SENSITIVE LAYER CONSISTING ESSENTIALLY OF A PHOTOGRAPHICALLYACTIVE PRODUCT FORMED BY: EXTRACTING FROM AN ETIOLATED PLANT MATERIAL APHTOACTIVE PROTOCHLOROPHYLL(ID)-APOPROTEIN BINARY COMPLEX WITH A BUFFERSOLUTION AT A PH BETWEEN 7 AND 10 IN THE PRESENCE OF OF AN AGENT TOPROTECT THE APOPROTEIN AGAINST DENATURATION AT A TEMPERATURE OF AT MOST5*C; ADDING TO SAID BINARY COMPELX AT A TEMPERATURE OF AT MOST 5*C ANATURAL OR SYNTHETIC POLYMERIC MATERIAL SELECTED FROM THE GROUPCONSISTING OR POLYETHYLENE GLYCOL, POLYVINYLPYRROLIDONE,TRIETHANOLAMINE, SACCHAROSE AND DEXTRAN TO FORM A PRECIPITATE;COLD-CENTRIFUGING SAID PRECIPITATE TO FORM A PRODUCT WHICH IS EITHER INCOMPLEX OR IN ASSOCIATION WITH SAID POLYMERIC MATERIAL; AND LYOPHYLIZINGSAID PRODUCT AT A TEMPERATURE OF AT MOST 5*C SO THAT THE DRIED FINALPRODUCT REMAINS PHOTOACTIVE AT ROOM TEMPERATURE, SAID PRODUCT FORMING APATTERN BY INFORMATION-WISE EXPOSURE TO LIGHT OF INFORMATION-WISEDIFFERENTIATIONS IN LIGHT-ABSORPTION AND FLUORESCENCE EMISSIONCHARACETERISTICS.
 2. The photographic recording material defined inclaim 1 wherein said polymeric material is polyethylene glycol.
 3. Thephotographic recording material defined in claim 1 wherein said supportis a transparent sheet.
 4. The photographic recording material definedin claim 1 wherein said support is an opaque sheet.
 5. A method ofrecording information which comprises information-wise exposing aphotosensitive product to light of a wavelength range absorbed by saidproduct to produce thereby a pattern of information-wisedifferentiations in light-absorption and fluorescence-emissioncharacteristics, said product being obtained by the steps of: extractingfrom an etiolated plant material a photoactiveprotochlorphyll(ide)apoprotein binary complex with a buffer solution ata pH between 7 and 10 in the presence of an agent to protect theapoprotein against denaturation at a temperature of at most 5*C; addingto said binary complex at a temperature of at most 5*C a natural orsynthetic polymeric material selected from the group consisting ofpolyethylene glycol, polyvinylpyrrolidone, triethanolamine, saccharoseand dextran to form a precipitate; cold-centrifuging said precipitate toform a product which is either in complex or in association with saidpolymeric material; and lyophilizing said product at a temperature of atmost 5*C so that the dried final product remains photoactive at roomtemperature, said product forming a pattern by information-wise exposureto light of information-wise differentiations in light-absorption andfluorescence emission characteristics.